1. Field of the Invention
The present invention relates to a method for manufacturing a golf club head and, more particularly, to a method for manufacturing an integrally formed high-strength golf iron head with a thin striking faceplate.
2. Description of the Related Art
Golf club heads includes woods, irons, and putters. Early woods and irons are generally made of stainless steel or carbon steel to increase the performance of the golf club heads. New steel-type cast materials have been continuously developed in recent years and have been used to manufacture golf club heads. For example, steel type alloys containing cobalt, molybdenum, or titanium generally has a high strength (the tensile strength is higher than 250 ksi) suitable for manufacturing golf iron heads.
Currently, golf iron heads are produced in the atmosphere by using a high frequency induction furnace to rapidly melt the cast materials. Next, the slag and gases in the molten metal are removed by slagging and refinery steps. Static gravity pouring is then carried out to obtain a golf iron head.
However, the cast materials for golf iron heads often include active metals (such as manganese, aluminum, silicon, cobalt, molybdenum, and titanium) that are apt to react with oxygen in the air. Thus, rigorous oxidation easily occurs during the procedures of smelting of the cast materials, increasing difficulties in melting and easily causing oxidative fire cracks due to reaction with air during pouring. As a result, appearance defects, such as sesame dot defects and black bean defects, are apt to be formed on the cast products of the golf iron heads. In worse situations, the reactive gas forms a large number of slag holes or blowholes in the cast products of the golf iron heads and, thus, adversely affects the tensile strength of the golf iron heads, limiting the thickness of the striking faceplates of the golf iron heads.
Namely, to assure that the striking faceplate of a golf iron head can meet the tensile strength standard for withstanding cannon shots of predetermined strength and times without damage, the thickness of the striking faceplate of a current integrally formed golf iron head is still too thick. Table 1 shows the tensile strengths and minimum thicknesses of striking faceplates of golf iron heads made of different materials by gravity pouring in the atmosphere, wherein the “minimum thickness” is defined as the minimum thickness of a striking faceplate having a strength capable of withstanding 3000 cannon shots at a speed of 50 m/s without damage (excluding the groove depth).
TABLE 1strikingtensileminimumstrikingtensileminimumfaceplatestrengththicknessfaceplate strengththicknessmaterial(ksi)(mm)material(ksi)(mm)NANO 5583.204501702.45303773.204501802.35304773.20HYPER17-42002.38620853.20AM3552102.3MS225982.85ES2302302.20M-9982.9041302302.154311002.8541302302.15ST-231023.20ES2352352.204311102.85SUP 102362.20LD-7451202.815-7 PH2402.2022051252.704552502.1017-4PH1402.7465 + (275)2702.05ST-221492.754752802.00
As can be seen from Table 1, to achieve the same cannon shot conditions, the tensile strength and the minimum thickness of each striking faceplate material are highly related. Namely, the minimum thickness can be smaller if the tensile strength of the striking faceplate is higher. Furthermore, given the above cannon shot conditions, the average minimum thickness (excluding the groove depth) of the striking faceplate of a current integrally-formed golf iron head is about 2.59 mm. For a striking faceplate having a higher strength (above 250 ksi), the minimum thickness (excluding the groove depth) has to be more than 2.0 mm. Thus, there is a bottleneck in reducing the overall weight of current golf iron heads.
Furthermore, rigorous oxidation also reduces the flowability of the molten metal in the shell mold, leading to a reduced yield of the cast products of golf iron heads due to insufficient pouring or resulting in gaps in the cast products of the golf iron heads due to cold shut. The tensile strength of the cast products of the golf iron heads is also adversely affected.
Thus, improvement to conventional methods for manufacturing golf iron heads is desired.